Reducing motor vehicle accidents is a perennial concern for health policy makers. Motor vehicle accidents cause more than 40,000 deaths and several million injuries each year, and are also the leading cause of death among children in the United States. While a large body of literature examines the impact of regulations and technological innovations, such as seat belts, airbags, and child safety seats, there has been considerably less work on the effect of traffic law enforcement.

In an upcoming issue of the Journal of Policy Analysis and Management, Dara Lee Luca, a Visiting Assistant Professor of Public Policy at the Harvard Kennedy School, examines the dramatic increase during the Massachusetts “Click-it-or-Ticket” traffic program in her new paper, Do Traffic Tickets Reduce Motor Vehicle Accidents? Evidence from a Natural Experiment. Using data to identify the causal impact of tickets on accidents, Luca found that tickets significantly reduce accidents and non-fatal injuries; a one percent increase in issued tickets led to a .28 percent decline in motor vehicle accidents. The article is currently available for free on WileyOnline and can be viewed in its entirety through the end of October 2014.

“I first became in interested in the topic when a couple of papers on traffic tickets came out on how towns in more fiscal distress issued more tickets,” says Luca. “There’s also the perception that traffic law enforcement officers are biased by personal preferences, such as race or gender, when they issue tickets. These papers made me wonder whether tickets actually achieve what should be their original goal, which is to deter reckless driving and improve road safety.”

More police officers tend to be stationed at areas and during periods with higher rates of traffic accidents, so that addressing the question is complicated by the issue of reverse causality. Further, while the ostensible goal of traffic tickets is to improve road safety, recent research has demonstrated that traffic tickets are often used as a tool to generate revenue for local municipality budgets. It has been unclear whether tickets fulfill their intended purpose of increasing road safety.

“I had no prior beliefs about whether tickets would actually affect road safety, so I was surprised to see that not only did tickets reduce accidents, the effect is quite clear-cut,” says Luca. “I also found some suggestive evidence that tickets have a larger impact on women than on men, as well as night drivers, which I thought was interesting.”

These results on the heterogeneous effects of tickets may help inform policy makers how to allocate enforcement in order to achieve the highest impact. Overall, the findings of this new study suggest that as unpopular as traffic tickets are among drivers, they do in fact help to reduce motor vehicle accidents.

Luca is a Visiting Assistant Professor of Public Policy at the Harvard Kennedy School, while on leave as an Assistant Professor of Economics from the University of Missouri. She is also a Research Associate at the Global Health and Population at the Harvard School of Public Health. Luca’s research investigates policy issues related to the economics of human capital accumulation - including health, education, and aging - both in the U.S. and globally.